Functional magnetic resolution imaging (fMRI) is capable of achieving millimeter spatial resolution in measurements of blood oxygenation associated with neural tissue activation in the brain. Electroencephalography (EEG) is capable of achieving submillisecond temporal resolution of the electrical activity. Many studies can now benefit from the synergy of these two techniques, but simultaneous recording is difficult at present. To fill this gap, we propose to design, prototype, and test an integrated system that will make it easy to record EEG in an MRI scanner during fMRI acquisition. To ensure better comparison for studies not requiring simultaneous recording, we will design the system to perform EEG studies as if they were being conducted in the magnet. In Phase I, we will build and test a 16-channel system, using a physical phantom to demonstrate feasibility. In Phase II, we will then construct a complete 256-channel system to include integrated head stabilization, specialized head coils, rapid and painless application of 256 EEG electrodes, ERP/fMRI experimental design and control software, joint EEG/fMRI segmentation and analysis software, and combined EEG/fMRI source-modeling software. The Phase II system will be tested with a dual EEG/fMRI phantom, as well as in human subjects with visual perceptual and attention experiments. PROPOSED COMMERCIAL APPLICATIONS: The proposed system will be attractive to any lab currently running fMRI experiments, or to anyone setting up a new fMRI lab who wants to include high-density EEG recording in the scanner. Its performance will surpass any other MRI-compatible system now on the market. Because of its fMRI/EEG capability and superior performance, the system will especially appeal to researchers in perception, motor control, and cognitive psychology, as well as clinicians evaluating epilepsy and other brain disorders.